All signs are pointing to the younger son.
- 60 times is overkill. A professional hit is efficient and clean. This was a crime of passion and personal.
- If the mom was cheating she would just go out and cheat out of view and hearing distance of her teenage son. Too much liability to do it in the same house where the boy can interrupt at any time. The son is the one who told the police that she said was going out. So how did we get to the mysterious visiting stranger? This is the tale of a teenager who is not very good at lying.
- Speaking of which, the cover story of a psycho vindictive killer who is out for the blood of the family is the perfect cover to stoke the protective nature of the father. It's also a good distraction to prolong looking at the son.
- The mom had defensive knife wounds, which means she put up a fight and definitely screamed but the son is upstairs, and couldn't find her?
- The police questioned the boy twice because they're probably are already suspicious.
!!!!
Not to mention the size of the person from the videos
Killer choosing to walk a half-mile instead of driving (likely didn't have access to a car, or didn't want to risk driving)
Convenience of hockey duffel bag(which belongs to the kid)